Re: [stella] 2600 Radial Pong / Joust Pong Update

Subject: Re: [stella] 2600 Radial Pong / Joust Pong Update
From: KirkIsrael@xxxxxxxxxxxxx
Date: 5 Jul 2002 16:03:43 -0000
(Sorry, forgot to send to the list...)

> > Currently my biggest issue is bounds checking.  I've been trying to 
> > keep it mathematical, i.e. comparing the vertical position to certain 
> > constants for the floor and the ceiling, but I keep getting some odd 
> > behaviorial results... 
> Floor and ceiling are easy enough if you'll sacrifice a few scans to a solid 
> playfield the same color as the background.  From the looks of the other 
> versions of JoustPong, you won't have a playfield graphic in the middle of 
> the screen either, so you could probably get away with using the same color 
> playfield [as background] for left and right as well.  Then it's just an 
> issue of trapping collisions, which has to be easier. 

Well, I think the problem is less detecting the condition as doing the 
right thing to correct it, at least in my case...usually some kind of 
manual repositioning, otherwise I think they risk being kind of wedged 
in place.  In general I recalculate the speed, then finally add the speed 
to the position, so the collision behavior has to integrate well with 

Also, I don't think I have any way of reading the horiz. position of 
the ball. (The players is no problem, since they don't move horiz. 
at all) So I was thinking I'd have to run "black" background as 
vertical bands on the far left and the far right, and then check 
for collisions there to see if someone scores. (Or I guess I could 
try the same using missiles as the bands...) 

Behold the 2600: even writing Pong can get kinda complex :-) 

> That was my plan, anyhow.  Course then when you start thinking about adding 
> variations on theme that do use a playfield, I suppose timing will rear its 
> head again.  I've already had to dip into a two scanline kernel...  Kinda 
> crappy wrt the player graphics.  But checking for four things every line was 
> just too many cycles, quickDraw or no quickDraw. 

What kind of things are you checking for every scanline, 
rather than every frame? 

"It is evident that the end of the world is fast approaching." 
     - Assyrian Tablet, c.2800BC

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